JP2932618B2 - Casting pin for aluminum casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a blanking pin used for casting aluminum.

<Conventional technology> There are two methods for casting aluminum: a gravity casting method in which casting is performed using the weight of molten aluminum, and a die casting method in which molten aluminum is ejected at a high speed by applied pressure.
Classified into types. The cast pin used in these casting methods is a mold part that prevents the molten aluminum from flowing around in combination with a mold in order to reduce the number of processed parts of the casting.

The cast pin is subjected to chemical corrosion from the molten aluminum in addition to the heat cycle between the contact with the molten aluminum and the cooling at the time of removal. For this reason, a steel material excellent in heat cycle and corrosion resistance is selected as the material of the cast pin.

However, since the molten aluminum is extremely active, the corrosion of the cast pins is remarkable, and it is not an exaggeration to say that the production capacity of the casting process is determined by the life of the cast pins. For this reason, although the cast pin manufacturer has attempted a heat cycle test of various steel materials and a nitriding treatment on the surface of the cast pin, sufficient results have not been obtained. In other words, surface treatment with good corrosion resistance and heat cycle resistance causes "galling" with the mold, which significantly reduces the life of the mold and the dimensional deformation of the cast pin due to the high processing temperature. There is a drawback that may occur.

<Problems to be Solved by the Invention> The present invention aims to provide a cast pin capable of overcoming the above-mentioned drawbacks and not only corrosion resistance, heat cycle resistance but also galling with a mold. Specifically, it is intended to cover the surface of the cast pin with a material having the above-mentioned properties.

<Means for Solving the Problems> That is, the cast pin for aluminum casting of the present invention is characterized in that the pin surface is coated with a hard carbon film having a thickness of 0.5 μm to 5 μm.

<Operation> Although the shape of the cast pin is often a simple rod, the rod diameter often changes in the middle.
In order for the D method to not impair the dimensions and mechanical properties of the pin base material, it is necessary to perform the coating in a temperature range of 500 ° C or less. Is preferred.

The conventional PVD method has problems in the adhesion and soundness of the coating, and the thermal spraying method cannot form a film.

As a raw material gas used for coating, a gas obtained by diluting a hydrocarbon gas with a hydrogen gas is suitable. It is also effective to introduce Ar gas to raise the excited state of the source gas.

As a means for generating plasma, either direct current or alternating current can be used, but glow discharge by high frequency (13.56 MHz) is most preferable. It is also effective to apply a DC bias voltage to the substrate in parallel with the RF glow discharge.

Regarding the coating thickness, if the coating thickness is too small, there is no effect of coating and no improvement in corrosion resistance is observed, and a coating thickness of 0.5 μm or more is required. On the other hand, the maximum film thickness is preferably as thick as possible from the viewpoint of corrosion resistance.

The introduction of an intermediate layer is also effective as a means for further improving the adhesion between the pin and the coating. Preferred materials for the intermediate layer include charcoal and nitride ceramics.

<Example> Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 The results of a corrosion resistance test (melting test) on molten aluminum (ADC12) are shown below.

Prepare a 10mm × 10mm × 70mm test piece (material: SKD11)
Hard carbon films were coated at various thicknesses and compared to uncoated materials. The test conditions were as follows. The test piece was immersed in a melt of ADC12 at 670 ° C. and moved up and down at a stroke of 30 mm and 90 times / min. 90min
After the test, the test piece was taken out and the state of erosion was compared. Table 1 shows the results.

Example 2 In a die casting process of ADC12, a test sample was put into an actual machine to evaluate its performance. The casting conditions are as follows.

Melt temperature: 680 ° C Shot cycle: 35-40sec Hot water speed: 55m / sec Product: Transmission case for automobile Pin material: SKD61 The performance was determined by the presence or absence of galling at every 50 shots. The test results are shown in Table 2.

<Effects of the Invention> As described above, according to the casting pin for aluminum casting according to the present invention, the surface thereof is coated with a hard carbon film having a thickness of 0.5 μm to 5 μm. It was recognized that it had excellent cycleability and also had excellent galling with the mold.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B22D 17/22 B22C 9/06

Claims (1)

(57) [Claims] 1. A steel pin surface having a thickness of 0.5 μm to 5 μm.
A cast pin for aluminum casting characterized by being coated with a hard carbon film.